Modern automated gas cutting torches are commonly equipped with features such as automatic ignition, automatic standoff control, kindling temperature detection, ignition and blowout detection, and neutral flame detection. Each of these features can be implemented using actuation and sensing mechanisms that should be reliable, economical, and resistant to the harsh operating environments created when cutting is performed (e.g. high heat, abrasive debris, particulate deposition etc.).
Kindling temperature detection has been successfully achieved using optical infrared (IR) sensors directed toward a work piece. While optical sensors are generally effective for such an application, they are extremely sensitive to abrasion and particulate deposition, and are therefore commonly mounted within a torch and directed down the torch's cutting oxygen orifice. One problem with this approach is that it cannot be implemented in cases where the diameter of a torch's cutting oxygen bore is too small to accommodate an optical sensor.
Automatic ignition in gas cutting torches has been achieved by temporarily re-routing a torch's fuel-oxygen mixture through the torch's cutting bore for a period of time sufficient to allow a flame, ignited internally, to propagate to the tip of the torch, where it is allowed to stabilize. This solution requires solenoids to be operatively mounted within the torch for adjustably routing the fuel-oxygen mixture.
Various techniques for automatic standoff control are known, each of which is associated with particular shortcomings. For example, capacitive standoff control techniques, such as those described in U.S. Pat. No. 6,251,336, rely on the assumption that a work piece (e.g. a steel plate) is a quasi-infinite surface. Such techniques therefore perform inconsistently when a cutting torch nears the edges of a work piece. Inductive standoff control techniques rely on perturbations in an induced, oscillating magnetic field around a work piece, and are therefore susceptible to undesirable cross-interference when two torches are operated near one another. Optical standoff control methods require sensors that must be mounted on the exterior of a torch, and are therefore susceptible to being obscured, scratched or otherwise damaged by debris during cutting. Mechanical standoff control methods that use whiskers or rider plates require large radii in which to operate. Such methods may therefore yield inconsistent results when performed adjacent a work piece's edges or near areas where two cuts meet.
It is apparent that current approaches for implementing certain advantageous features of modern gas cutting torches suffer from various inconsistencies of operation. Moreover, such approaches require additional electronics and hardware to be mounted on or inside of a gas cutting torch, which can substantially increase the cost of an automated torch system while diminishing the reliability of a system. It would therefore be advantageous to provide an automated gas cutting torch system that provides features such as kindling temperature detection, automatic ignition, and automatic standoff control, wherein such system is reliable, economical, and robust.